When I do a conversion, 64 dry quarts of potting soil = 2.48 cubic feet. But I remember that I had to buy more bags of potting soil than stated on the bag when I filled a 4'x4' bed.
I'm confused - are you thinking square ft when you should be thinking cu ft?
4'x4'x6" = 8 cu ft
4'x4'x8" = 11 cu ft
4'x4'x10" = 13 cu ft
4'x4'x16" = 21 cu ft
Dry soil also compresses under its own weight - especially when wet.
Yep, manufacturers definately know that dry soil fills more volume then wet, and sell it that way. If they sold it by weight, you can bet it would be the other way around.
Just found this calculator for doing this figuring for me: